A wireless communication device, such as a mobile phone device or a smart phone, may include at least one SIM. Each SIM may enable one or more subscriptions corresponding to RATs. Specifically, with respect to multi-SIM wireless communication devices, when all SIMs are active, the wireless communication device may be a Multi-SIM-Multi-Active (MSMA) wireless communication device. When one SIM in a Multi-SIM wireless communication device is active while the rest of the SIM(s) is/are standing by, the wireless communication device may be a Multi-SIM-Multi-Standby (MSMS) wireless communication device. The RATs may include, but are not limited to, Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA) (particularly, Evolution-Data Optimized (EVDO)), Universal Mobile Telecommunications Systems (UMTS) (particularly, Wideband Code Division Multiple Access (WCDMA), Long Term Evolution (LTE), High-Speed Downlink Packet Access (HSDPA), and the like), Global System for Mobile Communications (GSM), Code Division Multiple Access 1× Radio Transmission Technology (1×), General Packet Radio Service (GPRS), Wi-Fi, Personal Communications Service (PCS), and other protocols that may be used in a wireless communications network or a data communications network.
In a Single Radio Long Term Evolution (SRLTE) mode of operation, stacks of a first RAT and a second RAT may share the RF resources of the wireless communication device. In some cases, when a call for the second RAT (e.g., 1×) is being made, the wireless communication device may trigger an Extended Service Request (ESR) for the first RAT (e.g., LTE) before the call of the second RAT is processed. The ESR may indicate to the network associated with the first RAT that a fallback for the first RAT is in order. The ESR may delay the second RAT call for a time period (e.g. approximately 500 ms, which typically may be an approximate duration of the ESR). Given that the call of the second RAT (particularly 1×) may fail if not responded to within a specified time, the delay due to ESR may cause the call of the second RAT to fail when the wireless communication device attempts to respond to page of the second during the ESR of the first RAT. This effect is especially pronounced when the ESR takes about 600 ms. The second RAT may stand by to validate an Access Parameter Message (APM). Validating the APM can delay the call for up to 4 seconds. Often, the APM does not change.